This invention relates to a semiconductor device with a vapor-phase grown epitaxial layer, and to a method of manufacturing the same, more particularly, to a method for causing vapor-phase epitaxial growth, on the surface of a semiconductor substrate of silicon or the like, of GaAs or a like substance having a different lattice constant from that of the substrate, and to a semiconductor device having the vapor-phase epitaxial layer.
It is well known in the art that when fabricating a semiconductor device, an epitaxial layer is formed on a semiconductor substrate by causing vapor-phase growth on the substrate surface of a semiconductor having a different lattice constant from that of the substrate.
For instance, a Group III and V element compound semiconductor, e.g., GaAs or InP, is epitaxially grown on a semiconductor substrate, such as a silicon substrate. When a semiconductor of GaAs, InP, or a like compound is epitaxially grown on the silicon substrate surface, there is a lattice mismatch factor with respect to the silicon constituting the substrate. This factor is 4.1% in the case of GaAs and 8.1% with InP. Therefore, if a GaAs layer is formed on a silicon substrate by growing GaAs thereon, the resultant epitaxial layer will have considerable defects and inferior surface shape.
With the aim of solving this problem, it has been proposed to form an intermediate layer as a super-lattice constitution element between the silicon substrate and GaAs layer, so as for this intermediate layer to absorb the lattice mismatch between silicon and GaAs, this method being disclosed in Japanese Patent Laid-Open Publication Sho 61 (1985) - 91,098.
However, where such an intermediate layer is formed, mixture crystal and very thin films must be controlled repeatedly in the epitaxial layer formation process, and complicated process control is required.
It is taught to cause growth of GaAs directly on a silicon substrate, and it is well known that a mirror surface can be obtained by means of a two-step growth process. In this case, however, a resultant hetero-epitaxial layer contains a large number of transitions and other defects.
For example, when a thin film of GaAs is formed on a silicon substrate, warping of the resultant wafer results when a high level of heat is applied thereto, due to silicon and GaAs having different coefficients of thermal expansion.